The chromium-catalyzed synthesis of 1-hexene from ethylene constitutes a commercially significant process for the selective preparation of this alpha olefin, which in turn is useful for preparing a range of polyolefins when employed as a comonomer with ethylene. A widely reported chromium catalyst system for the selective production of 1-hexene comprises chromium(III) carboxylates (e.g. tris(2-ethylhexanoate) chromium(III) (Cr(EH)3)), a pyrrole compound, and a metal alkyl.
Many oligomerization catalyst systems for the selective production of 1-hexene contain a chromium compound, a pyrrole compound, at least one metal alkyl, optionally a solvent, and optionally additional components, which can be combined in various ways and in various ratios to afford the catalyst system. Some catalyst system preparative methods appear to rely on the presence of particular solvent to stabilize the catalyst system. Typically, any method of preparing, activating, and using a catalyst system may present challenges with respect to its particular preparation, activation, and stability, as well as to the activity and selectivity provided by the catalyst system.
Therefore, it would be useful to discover and develop new oligomerization catalyst systems, new methods for preparing the oligomerization catalyst systems, and new methods for using the oligomerization catalyst systems for preparing an oligomerization product that might provide greater efficiency and cost effectiveness. New oligomerization catalyst systems and methods for preparing the oligomerization catalyst systems that might afford greater activity, increased efficiency, lower costs, increased selectivity to C6 products (or to 1-hexene), and/or increased 1-hexene in the C6 product fraction would be desirable.